Internal combustion engine



K J. s. FRAzER INTERNAL' cQMBUsTIoN ENGINE 4 Sheets-Sheet 1 Nbv. 21, 1939.

Filed Aug. 25, 1937 J. s. FRAZER 2.180.898

Nov. 21, 1939.

' INTERNAL GOMBUSTION ENGINE i 4 Sheets-Sheet., 2

Filed Aug. 25, 1937 Snnentor n A QQ l K l fb/ e! l Gttomeg NOV-'21, 1939- J. s. FRAzr-:R

` INTERNAL COMBUSTON ENGINE I Fld Aug. 25, 1937 4 Sheets-Sheet 3 Nov. 2l,v 1939.

J. s. FRAzER INTERNAL COMBUSTN ENGlNE Filed Aug. 25, 1937 4 sheets-sheet 4 Patented Nov. 21,1, 1939 UNITED; STATES 'PArENr .oFF-lcs l 'm'.rEaNAL connivencia sNcrNn Jamcs S. Frazer, Earlevilleflld. application Anims z5, 1931, serial No. 160,898 y is claims. (ci. 12a- 51)l This invention relates to improvements in internal combustion engines, capable of general use but particularly intended for the propulsion of aircraft, and has generally in view to provide an enginewhich, for any-given horsepower, is

of exceptionally light weight; Ywhich is of simple,

, sturdy construction and of Arelatively low DIO' -duction, operation and maintenance cost; which is so designed that it may be disassembled quickly and easily for the repair or replacement of parts, and equally as readily reassembled; which possesses long life and isthoroughly reliable and highly emcient in operation; which presents a comparatively small frontal area; and which is 15, of such shape that` it may readily be mounted Within the wing structure of an aircraft, thereby totally lto eliminate, or substantially totally to eliminate, resistance t0 flight of the aircraft insofar as the engine is concerned. Preferably the present engine is oi' the opposed pis n, dual crank shaft type operating on'` the two 'stroke cycle, mechanical fuel injection, in'- ternal vaporizing, high pressure ignition principle, whereby valve, valve mechanism and ignition troubles, such as have heretofore been experienced in connection with engines having valves and electrical ignition systems, are eliminated and reliability is correspondinglyincreased.`

i However, the engine may be constructed tov operate on the fourfstroke cycle-principle, and wheth-Z er constructed to operate o'n thiwor the two stroke cycle principle, may be designed to employ either, solid or carbureted fuel, and may be equipped with an electrical ignition system. In any event, a crank case is provided at each nd of the cylinder, 'orthe series of cylinders, as the case may be, and said crank cases are separate from the interposed cylinder or cylinders and 1 are connected together by tie rods, whereby the 40 engine may be quickly and easily assembled and disassembled. In this connection, a special object of the inventionis to provide novel, practical means for maintaining the crank cases at all times spaced apart a single, definite amount re- I gardless of longitudinal expansion and contracg tion ofthe cylinder or cylinders, or, conversely, to provide a connection'between the crank cases permitting longitudinal expansion and contraction of the interposed cylinder or cylinders without affecting the definite spaced apart relationship of the crank cases, whereby longitudinal expansion or. contraction of the cylindervor cylinders does not aiect thegear connection which is provided between theecrank shafts Journaled inthe crank cases, nor seriously aiIect the opera- .tive relationship -i`between. other cooperating" parts, such as the 'fuel pumps and their operating shafts, which are, or'may be, carried by or'convnected with the cylinder or cylinders and one or both of the crank cases, respectively. 5 Another special obiect oi the invention, in the case of an engine' of vthe character mentioned and constructed tocperate on the two stroke cycle principle, is to provide a scavenging and` combustion air inlet port which is so designed 10 as not to impart turbulence to the air iriitiallyi` admitted' to the cylinder, but to impart turba-"1` lance to the -air last admitted to the cylinder,

frontal areaof the crank cases and the cylinder 25 o r cylinders. i

Another special object of the invention is to provide a novel sectional crank shaft construe? tion-to permit the use of anti-friction ball or 'n-V'rlierf'bearings for the crank shafts and to permit 3o the number of .engine cylinders or units to be readily increased or decreased.

With the foregoing and other objects in view, which will become more fully apparent as the nature of tlie invention is better understood', the 35 in the novel features of construction, combination land arrangement' of parts as y will be herleinaftermore fully described, illustrated in the accompanying drawings and dened in the appended claims. 40,

'Inthe drawings, wherein like characters of reference denote correspondingparts in the different views: i

Figure 1 is a front elevation of an engine constructed in accordance with one practical embodiment of. theinventlon.. I

Figure 2 is a central longitudinal section through l.the engine.

` gles to F18. 2'.

Figure 4'is a longitudinal section taken ap- H proidmately on the line I-l of Fig. 2. l Figure 5 isa detail sectional view showing thel air in'letports of onebf the `cylinders. I y 55 `Figure 3 is a longitudinal section at right an- 50 ofthe engine.`

= inlet ports.

the lines 9 6 and 1-1, respectively. ofFig. 5.

AFigure 8 is a transverse section taken approxi- ,mately on the line 8-8of Fig. 2'. '5 Figures 9` and 10 are cross sections through the exhaust and'V the intake manifolds.' respectively. of one of the Cylinders;

Figure 11 is a Adetail longitudinal section view through one of the sectional crank shafts Figure l2 is a detail cross section showing the splined connection between the separate sections of one of the crank shafts. Y

' Figure 13 is an enlarged longitudinal section'v 15,through one of the pairs of the fuel injection pumps and their actuating and stroke regulatingv means.V Y I l Figure 14 is a detail sectional view of one'of the `fuel injection nozzles. I e

Figure 15 is a'sectional view showing a power .take-off gearing arrangement for c oaxiaL. op-

positeiy rotating propeller shafts; 'and' l Figure 16 is. a fragmentary sectional Vview through one As will be understood, the present engine may comprise only a single cylinderorfa plurality of cylinders. Itv will also be understood that the cylinders may be finned for air -cooling or jacketed for liquid cooling, and that-the engine may be installed to operate in avertical. horizontal or-inclined position.V In the present instance the engine isillustrated as' being of the multiple cylinder type comprising any desired number of cylinders Il which, in accordance'with the invention, are disposed-in a common plane in to side, spaced, parallel relationship.

Each cylinder is open at each end, and at each end of the series of cylinders is a crank case II having in its inner wall I2 a series of openings in which the adjacent ends of the cylinders are neatly fitted whereb; the cylinders are held effectively against any lateral movement relative to each other. The -end portions of said cylinders are, however, longitudinally slidable relative to the crank cases; through said openings. To prevent leakageY of oil from the crank cases around the end portions of the cylinders, the latter preferably are embraced by sealing rings I2' of rubber or other suitable material which may be seated in grooves in the walls surrounding the openings in the crank cases through which the end portions of the cylinders extend.

In order to maintain the two crank cases II,

ber of spacing elements in the form of elongated A spools I3 are interposed between the adjacent or inner walls I2, I 2 of said crank cases. 0n the other hand, in order to clamp the two crank cases against the ends of the spools I3, thus to tie said crank cases firmly together, tie rods' I4 are extended through said spools, through crank shaft bearing housings I5 which are cast of the cylinders showingspiral air s gear 22 on each crank shaft and ashaft 23 carrying a pair of bevel pinions 24 meshing, respectively, with the gears 22, 22.

'disposed at one end of the series of cylinders III in the plane of'said cylinders, and a `feature oi!- side v Il in definite, spaced apart relationship, a num- I A v 2,180,898 Figures 6 and- 'Z are detail cross sections on g mations are located, it follows that -while the :cylinders thus are held effectively. against any `longitudinal shifting movement bodily relative to the crank-cases, the end portions of said cylinders are, nevertheless, free to move longitudinally relative to the crank cases under expansion and contraction.

are crank shafts I9, I9 each having a plurality of cranks, one related. to each cylinder, while within each cylinder isa pair of pistons 20, 20 which are connected by rods 2 I 2I to the related -cranks of the cylinders develops in oppositeV directions from the middle portions thereof Where said jforof Uthe respective crank shafts, the crank shafts Y ing compression periods of the engine and simultaneously outwardly during firing periods o f the engine.

In the present,instance the gearing connecting the two crankshafts I9, I9 comprises a bevel This gearing is saidgearing isA that it is 'confined substantially within the frontal area ofthe engine, which'is of importance in reducing air4 resistance'if the engine is used in an aircraft. The pairs ofbevel gears 22, 24 are enclosed within housings 25 vformed with or fastened to the crank cases II,

and the shaft 23 isjournaled in suitable bearings, preferably of the anti-friction ball or roller type,

mounted in said housings 25. Inv one ofthe hous- 1 ings 25 is suitably journaled a power. take-'off or propeller shaft 26 .havinga bevel gear 21 meshing with the related bevel pinion 24 on the shaft 23, or, alternatively, with a separate bevel gear on the shaft 23,' as may be desired.v In this connection the gear-2`| obviously .may be of any de- 4sired diameter' to afford'any desired reduced speed ratio between the propeller shaft and the engine crank shafts.

It is desirable that all, orat .least some, of thev 1 main bearings of the crank shafts I9, .I9 be of the antifriction ball or roller type. In the case of an ordinary, one-piece crank shaft it obviously is not possible to employ a ball orv roller bearing between adjacent crankl portions of the' shaft because of the annularly continuous nature of the bearing and because it can be placed on a shaft, or' a shaft can be inserted therein, only by relative endwise movement of the bearing and the shaft, which, in the case of a one-piece crank shaft, is prevented by the cranks. Accordingly, the present crank shafts I9, I9, preferablyare formed in separate sections each comprising one or more cranks, and'saidsections are formed at serting the male portions ofY adjacent crank." sections in said female portions.V Another ad-A vantage of this sectional crank shaft construction is thatl a given crank shaft comprising any desired number of cranks may be assembled from the present crank shaft sections, thus avoiding the necessity of manufacturing crank shafts embodying different numbers of cranks for use in engines having different numbers of cylinders, as would be necessary if the crank shafts were of one-piecel construction. In this connection, by having twenty-four evenly spaced splines between each two crank shaft sections it obviously is, possible to properly angula'rly space the respective cranks to form shafts for two, three, lfour, six or eight cylinder two-stroke'engines.

-While any or all of the crank shaft main bearings may be of either the usual journal type `or y of. the anti-friction ball or .roller-type, it is preferred that said two types of bearings be alternated along the length of each crank, as illustrated in Figs. 2 and 9. In any event, the bearing housings i5 preferably are recessed as illustrated in Figs. 4 and 9ito receive and hold the` removable halfpo'rtions'orcaps 3i of said bearings. The ends of the caps 3E are faced to iit between corresponding facings on the cheeks H58 formed by recessing the bearing housings l5, and said bearing housings, including the cheeks i5, are connectedA with the side walls of the crank casesby webs 32 disposed forwardly and rearwardly well beyond the crank shaft center line.

Moreover, the related tie rods I4 preferably are employed to secure said bearinghalf-portions in said recesses, thus simplifying the engine construction and at the same time assuring rm, rigidi support Aof the crank shafts within the crank cases, especially since the bearing housings, which' extend from the inner walls `I2 of the crank cases,

are reinforced by transverse tie rods 33 extend-A located closely adjacent to the shaft journals,-

said tie rods may extend from top to bottom of the crank cases normal to the cylinder axes. On the other hand, inthe case of such of the main bearings as may be of the -ball or roller type, the tie rods preferably are formed in two parts which meet in lugs resting on or integral with the bearingcaps 3i and from said lugs are inclined inwardly so that theirouter ends cooperate with the top and bottom walls of the crank cases at points more nearly overlying and underlying the crank shaft journals. By exerting inward pressure onthe cheeks l5a of the'bearing housings and thereby. holding the facings on the inner Y sidesof said-cheeks-rmly engaged with the facings on the 4ends of the bearing caps, any exing of the back portions of the journal bearings is effectively avoided. y Y I Further regarding the crankshafts I9, I9, these preferably are of hollowconstruction as illusvtratedfin Fig. 9 for best heat treatment in their manufactureiand to afford a convenient means of 'conducting lubricant to the crank shaft main bearingsVthe connecting rod bearings and the piston wrist pins.- 4.The'ends of the hollow main and crank portions of the-shafts'are closed by pairs of disks 34 connected together d held hollow shaftl portions in any desired manner. Ducts 3E connect the respective hollow portions and other ducts lead from said portions to the main andconnecting rod bearings and through the connecting rods to the wrist pins.

As aforesaid, the engine is of the two-stroke cycle, mechanical fuel injection type in which air is highly compressed between related pistons upon inward ymovement of the same and in which explosions are produced. for driving the pistons outwardly by the injection offuel under high pressure into the combustion spaces between the pistons when the latter are in, or substantially are in, their innermost Positions. Near one end of each cylinder is an annular series of ports v31 which are uncovered by the related piston for the admission of air` to the cylinder when said piston is in its outermost position,` while near the other end -of each cylinder, preferably at both the 'top and the bottom thereof, are ports 3B which are uncovered by the other piston for the escape .of burnt gases from the cylinder when the latter piston is in its outermost position.

In order to assure the supply of a sufficient f volume of scavenging and combustion air to each cylinderupon completion of outward movement of the related pair of pistons 2li, 2|! each crank case H has mounted thereon, outwardly ofits crank shaft and in alinement witheach cylinder l0, an air cylinder 39. In other words, therer are two air cylinders 39, one'at each end of the engine, related to each power cylinder l0, and from each related pair of these air cylinders air conduits 40 lead to manifolds or receivers 40', from which branch conduits 40a lead to the ports 31 of the related power cylinder. Preferably the conduit from one air cylinder'leads to the ports at one side of the middle of the cylinder and the conduit from the other air cylinder leads tothe ports at the other side of the middle of the cylinder to assure a substantially uniform supply of air to the cylinder circumferentially thereof.

Within each air cylinder 39 is a piston 4| which is connected by a rod 42 to the related connecting rod 2l so that as each piston 2li moves foutwardly in its power cylinder :i0 the-related piston 4i moves outwardly in its related air cylinder. thereby compressing air in the latter cylinder and in the conduit 40 so that when the air ports 31 are' uncovered by the related piston i0, a charge of scavenging and combustion air under pressure rushes into the cylinder (I0. In this connection, any suitable valve means may be pro-- vided to admit afresh charge of air to each air..

cylinder 39 upon, subsequent inward movement of the related piston4l. Also vin this. connection, a

feature of theinvent'ion resides in forming the ports 31 of each cylinder I0 as shown in Figs. 5f

to'l of the drawings, so that the air initially en.- tering each cylinder Ill does not have turbulence imparted thereto and therefore doesI not mix `readily with the burnt gases contained in said.

cylinders, but serves as a uid piston for the expulsion of the burnt gases, and so thatturbuy-lence is imparted to the air'last admitted to each A cylinder, whereby its thorough admixture with whereas', that portion 44 of each port 31 which .lastly is'uncov'e'red by'the related piston, has its in. place' by bolts 35, andoil is sup said sidewalls-inclined to the medialfradial plane of 3, so that the exhaust ports 38 of each cylinder are uncovered .suiliciently in advance of uncovering of the air inlet ports 31 to permit the pres- 15 sure of the burned gases in the cylinder to become equal-to, or lower than, the pressure of the 'scavenging air which subsequently enters the portail. Thereby thorough scavenging is effected. Moreover, since the exhaust ports are 20 closed in advance -of the intake portsthere isY obtained in each cylinder Va supercharge of air.

While fuel may be injected into the cylinders Il! in any desied manner, it` is preferred that the same be injected in a'plurality of separate 52B jets at points spaced circumferentially, of each cylinder, thus to assure a thorough intermixture ofthe fuel and air within the very short period of time allowed 'for this purpose. There may be a singl.l pumpor fuel supply conduit for each cyliii) inder communicating with the latter through a plurality of circumferentally spaced openings, or there may be a plurality of fuel pumps or supply pipes, one individual to each nozzle'or opening. In the present instance each cylinder I is a illustrated as being equipped with two fuel pumps, designated generally as 45, each communicating'with the cylinder. through a pair of nozzles, designated generally as 46, spaced ninety .degreesapart V Y 'Ihe fuel pumps 46 may be of any suitable type vand may be actuated in any suitable manner. In the present instance the pumps of veach pair are located directly above and below the related' by any possibility of engine cylinder pressures affecting the fuel pumps is avoided. In this connection, andif desired, another-check valve 52 may be provided in each pipe 5I adjacent to the 4related fuel nozzle 46.

Fuel supply lines are designated as 53 and are connected by branch pipes 54 with ports 55 at the inner .ends of the fuel pump cylinders,

the said ports 55 being disposed to be uncovered by the pump pistons 46 as the latter move outwardly to admit charges of fuel to thepump cylinders, and to be covered by the'puinp pistons as the latter move inwardly, whereby the admitted fuel charges are forced to the related pair of fuel nozzles.

The pump pistons are movable outwardly by suitable springs 56 and are movable inwardly b y suitable cams on cam shafts 51 mounted in the crank cases il and driven in properly timed' re- --lationship to, and from, the engine crank shafts through suitable gearing, the arrangement ofsald cam shafts and cams beingsuch, as shown, that the pistons of each pumparedriven inward alternately. v

Between each pump piston and its related cam is a mechanism of known type for varying the amount o f fuel-injected by the pump by regulating the piston stroke while maintaining .a constant lead and durationof the injection period for all engine loads. As best illustrated in Fig. 13, each' mechanism comprises a cam followv within, the related crank case I I; a guide sleeve 60 mounted on the related crank case in alinement with the related pump cylinder-and having reciprocable therein a member 6l connected-to the related pump piston; and a link 62 pivotally engaged at one end with the inner end of themember 6I and' slidably engaged at its other the link 62 toward the pivot Vofthe arm 59 the stroke of the related pump piston is reduced. Y L On the other hand, by moving the last mentioned end with the related camV follower arm 59. Obviously, by `moving the last mentioned end of? `l0 er 59 in the form of an arm pivoted at one end endof saidlink away from the pivot ofthe arm4 Y 59 the stroke of the pump piston obviously is increased.

y Novel meansr are provided in the present iii-.-

stance for adjusting the links 62. For each link said means comprises a screw 63 mounted in the related crank case; 'a link connecting said may be moved toward or from the pivot of said arm;A and a gear 65 mounted for rotation and held against longitudinal movement relative to the crank case -and having the screwl 63 threaded therethrough; Thus, by rotating thegear 65 thejscrew 63 may be longitudinally adjustedto move the end of the link 62 adjacent to the cam follower arm 59 toward or from the ypivot of said arm. Related to each set of corresponding gears 65 is a shaft 66 having thereon gears 61 one in mesh with each of the gears 65 of the set, so that by rotatably adjusting any given shaft 66 all of the gears 65 of the related setare rotated in 4unison to impart corresponding adjustments to the 'related set of links 62. Y l

The nozzles 46 are of -novel.construction and are designed to remain closed against engine cylinder pressures and to be opened by pressure of the` fuel supplied thereto by the fuel pumps 45. As illustrated in detail in Fig.` 14 of the drawingspea'ch nozzle 46 comprises abody 68 having an axial bore 69 closed at its outer end by a plug 16 and opening at its'inner end into a fuel chamber 1I within the inner end portion of said body; a small' orifice 12 for discharge of fuel from said chamber 1l through the inner end of the body 66; a piston 13 within the bore 69 having a reduced end to enter. and close'the orifice 12; a coil spring 14 interposed between the outer end of the piston 13 and the plug 1liv and tending constantly to move said piston inwardly to cause the reduced inner end of the piston to close' the orifice 12; and a duct 15 leading tothe chamber. from the fuel supply pipe 5| connected with the body 66..

'rnc body n is attached to 'a cylinder boss 1s and theorifice 12 at the inner end of said body is disposed to discharge into the cylinder. There- 1 piston 13 the highest pressures developed within the engine cylinder are incapable of moving said piston outwardly against the force of the spring i4. On the other hand,A due to the relatively" cylinder lll to upper and lower exhaust mani- 15 folds '58, are divided to provide spacesr to accomniodate the fuel pump mechanisms. The air conduits 'til leading from the air cylinders 35 to the air inlet ports 3l may be similarly divided. Preferably, however, the two air conduits from the go two air cylinders 39 related to each power cylinderl extend, respectively,l approximately onehalf the distance around the power cylinder, as illustrated in \Fig. 10, to provide the spaces necessary to accommodate the fuel pump mecha- '25 ,nisms from the two air cylinders is -delivered uniformly to the power cylinderat opposite sides thereof.

In Fig. of the drawings is illustrated a practical power take-o gearing to be used in lieu.` of 3i) the gearing shown in Fig. 2 when it is desired to drive coaxial propeller shafts in opposite directions. As in Athe case ofthe gearing illustrated in Fig. 2, the crank shaft i9 carries a bevel gear 22 whichmeshes with a bevel gear M on the shaft 23. However,instead of the bevel gear 2l on the 'propeller shaft 26 meshing with the bevel gear Z4 as in the Fig. 2 arrangement, said bevel gear 21 meshes with a separate bevel gear 79 on the shaft 23 and a third bevelgear 86 on said 40 shaft 23 meshes with a. bevel gear 8i on a second propeller shaft 82 which is hollow and telescoped over thefirst mentioned propeller shaft 2t. The gears 19 and B0 face oppositely. Therefore, the two propeller shafts 26 and 82 are driven in opposite directions either at equal speeds or a't 'different speeds, depending upon the relative diametersof the gears 2li, Eil and B, 8l.

From the foregoing description considered in connection with the accompanying drawings it V is believed that the construction, operation and advantages vof the present engine will be clearly understood. It is desired to emphasize, however, the simplicity of the construction; the fact that the cylinders are free to move at their ends relative to the crank case without affecting the spaced apart relationship of the crank cases or the gearing connecting the crank shafts, or the connec` pression, thus permitting the use of a higher.

compression ratio and a more elcient combus tion cycle than heretoforehas been considered practicable; the provision for utilizing anti-fric- -65 tioncr'ank shaft main bearings; the provision for building up crank shafts having different numbers of" cranks from thecrank shaft sections; the provision f or supplying air to the cylinders in the manner described; the novel gearing connect- 70 ing the crank shafts, and therelativelysmall frontal area. of the engine permitting it readily to'. be mounted in a horizontal position within the wing structure of an aircraft. Itis further desired to point out that while only a single struc- 76 .tural embodiment of the invention has been il- Moreover, by this arrangement the air lustrated and described, the features comprising the invention may be embodied, entirely or in part, in engines having different structural emport areas within given distances longitudinally 10 of the cylinders. As will be understood, these helical slots 31a may have the portions thereof corresponding to lthe portions 43 and 46 of the ports 3l, formed asdescribed in connection with said portions 43 and M of said ports 31.. '15

. Iclaim: t

1. An internal combustion engine of the opposed piston type comprising a cylinder, a crank case at each end of said cylinder, spacing elements between said crank cases, andtie rods 20 clamping said crank cases against the ends of said Spacing elements, the ends of the cylinder being freely movable longitudinally relative to the crank cases.

2. An internal combustion engine of the op- 25 posed piston type comprising a cylinder, a crank case at each end of said cylinder, spacing elements between said crank cases, tie rods clamping said crank cases against the ends of said spacing elements, the ends of the cylinder being 304 freely movable longitudinally relative to the crank cases, and means between at least one of said spacing elements and a medial portion of the cylinder holding the medial portion of the cylinder against longitudinal movement relative 35.

to the spacingelements and the crank cases.

3. An internal combustion engine of the opposed piston Atype comprising a cylinder, a crank case at each end of said cylinder, the ends of the cylinder being freely movable longitudinally rela- 40 tive to the crank cases, means independent of the cylinder holding the crank cases in a definite spaced apart relationship, and aconnection between a ,medial portion of the cylinder and said means Iholding the medial portion of the cylinder 45 against longitudinal movement relative to said means and the crank cases.

4. An internal combustion engine of the opposed piston ty'pe comprising a cylinder, a crank case at each end of said cylinder, spacingele- 50 ments between said crank cases, tie rods clamping said crank cases against the ends of said spacing elements, the nds oi. the cylinder being freely movable longitudinally relative to the crank cases, and interiitting formations on medial-por- 55 tions of the cylinder` and said .spacing-elements, respectively, holding the medial portion of the cylinder against longitudinal movement relative to said spacing elements and the crank cases.,

5. An internal combustionl engine of the opposed piston type comprising a cylinder, a crank case at each'. end of said cylinder, the ends of. the cylinder fitting into said crank 'cases and being freely movable longitudinally relative thereto, tie rods and means cooperating therewith holding the crank cases -i'n a denite spaced Y apart relationship independently of the cylinder, and crank shaft half-bearings in said' crank cases, the tie rods extending through said halft Y bearings and serving to hold them operatively p ositioned within saidfcrank cases. 6,'An internal combustion engine of the, cpposed piston type comprising aA cylinder, a crank case at each end of said cylinder, .Crank Shafts within said crank cases, a pair of pistons within 75 Y said cylinder connected tok said crank-shafts, re-

spectively, crank shaft main bearingslincluding caps, tie vrods connecting the crankjz'cases together andholdingthe crank shaft'r'nain bearing caps in operative positions, and othenztie -rods extending transversely lrelative toy saidl firstmentioned tie rods between opposite side walls.

.of eachcrank case adjacent tofsaid crank shaft 1 main bearings, there being integral'onnecting formations between the'main-bearings and the side/walls of the crank cases;-

'1,4 In an internal combustion enginefna'cylinder, a crank case, a crank shaft within said crank case, main bearings for saidvcrank' shaft, a piston within said cylinder connected to said crank i shaft, and tie rods connecting together opposite side walls of said crank case, said tie rods being located adjacent to said niain'bearings at the sides thereof remote from the cylinder and ex- .tending transversely relatively to the axes of the cylinder, land the crank shaft, there being integral web connections. betweenthe main bearings and the crank case sidewalls.

' l 8. In an internal combustiongengme of the op-'V posed piston type, a cylinder, arcrank case at each end of said cylinder, a crank shaft within each' crank case, main bearings within each crank case forthe crank shaft therein, tie rodsconnecting the crank cases together" and extending through related main bearings'in the "respective crank cases, and other tie rods connecting together opposite side walls of each crank case, said last mentioned tie rods being locatednadjacent to said main bearings at thesides thereof -remote from the cylinder and extending transversely relative to the axes of the cylinder andthe .crank shaft, there beingintegral web connections lbetween the main bearings and the crank case-'side walls.

Qt In an internal combustion engine of the opposed piston type, a cylinder, a crank case at each end of said cylinder, a fuel pump mechanism adjacent to said cylinder, and an exhaust conduit extending yfrom said cylinder and divided to extend around said fuel pump mechanism.

10. An internal combustion engine of the opposed piston type comprising a cylinder, a crank case at each end of said cylinder, spacing means between said crank ,caSes, means clamping said crank cases against s'aid spacing means, ythe ends of the cylinder being freely movable longitudinal- 1`y relative to the' crank cases, and means holding the medial portion of the cylinder against longitudinal movement relative to said spacing means.

' 55 1l..4 An internal combustion engine of the opposed piston type comprising a cylinder,r a crank case at each end of said cylinder, spacing means between said crank cases, means `clamping said .crank cases against said spacing' means and hold- A.ing the latter .operativelyV positioned between the crank cases, the ends of the cylinder being freely movable longitudinally relative to the crank cases,

and means holding the medial portion of the cylinder Vagainst longitudinal movement relativeto said spacingmeans..V

l2. An internal combustionengine of the opposed piston type comprising a cylinder, a crank case at each end of said cylinder, spacing means between said crank cases, means clamping said crank cases against said spacing means, the ends.

'of the cylinder extending into the crank case and being freely movable longitudinally relative thereto, and means holdng'the medial portion of the cylinder against longitudinal movement relative to said spacing means.

'13. An internalrcombustion'engineA of the opposed cylinder type comprising a cylinder, a' crank case at each end of said cylinder, spacing elementsA between said crank cases, tie rods clamp- 'ing said crank cases against the ends of said spacing elements and holding the latter operatively positioned between the crank'cases, the ends 'of the 'cylinder extending into the crank cases `and being freely movable Vlongitudinally relative thereto, and means holding themedial portion ofjthe cylinder. againstlongitudinal 4 movement relative to said spacing elements.

-l4. An internal combustion engine of the op- 'posed piston type comprising a cylinder, a crank Y case at each end of said cylinder, spacing means between said crank cascs,rmeans clamping said crank cases against said spacing means, the ends of the cylinder `being freely movable longitudinally relative to the crank cases, and means between the cylinder and said spacing means holdingthe medial portion of the cylinder against longitudinal movement relative to said spacing means.

l5. An internal combustion engine of the op- 

